Transactions of Nanjing University of Aeronautics & Astronautics
Volume 31,Issue 5,2014 Table of Contents
2014, 31(5):463-477.
Abstract:
The friction and wear properties of amorphous carbon nitride (aCNx) coatings in water lubrication were reviewed. The influences of mating materials and tribological variables such as normal load and sliding speed on the friction and wear properties of the aCNx coatings were analyzed. It was indicated that the specific wear rate of the aCNx coatings was related to the hydration reaction of mating materials with water. If the mating materials were easily hydrated, the specific wear rate of aCNx coatings was low. The wa ter lubricated properties of the a-CNx coatings were better in comparison to the aC coatings. The aCNx/Si based non oxide ceramics tribo pairs exhibited the lowest friction coefficient and wear rate. To describe their friction and wear proper ties at the normal loads of 3—15 N and the sliding speeds of 0.05—0.5 m/s, the wear-mechanism maps for the aCNx/SiC (Si3N4) tribo pairs in water were developed.
The friction and wear properties of amorphous carbon nitride (aCNx) coatings in water lubrication were reviewed. The influences of mating materials and tribological variables such as normal load and sliding speed on the friction and wear properties of the aCNx coatings were analyzed. It was indicated that the specific wear rate of the aCNx coatings was related to the hydration reaction of mating materials with water. If the mating materials were easily hydrated, the specific wear rate of aCNx coatings was low. The wa ter lubricated properties of the a-CNx coatings were better in comparison to the aC coatings. The aCNx/Si based non oxide ceramics tribo pairs exhibited the lowest friction coefficient and wear rate. To describe their friction and wear proper ties at the normal loads of 3—15 N and the sliding speeds of 0.05—0.5 m/s, the wear-mechanism maps for the aCNx/SiC (Si3N4) tribo pairs in water were developed.
2014, 31(5):478-483.
Abstract:
To cope with the problems that edge detection operators are liable to make the detected edges too blurry for synthetic aperture radar (SAR) images, an edge detection method for detecting river in SAR images is proposed based on contourlet modulus maxima and improved mathematical morphology. The SAR image is firstly transformed to a contourlet domain. According to the directional information and gradient information of directional subband of contourlet transform, the modulus maximum and the improved mathematical morphology are used to detect high frequency and low frequency sub-image edges, respectively. Subsequently, the edges of river in SAR image are obtained after fusing the high frequency sub-image and the low frequency sub-image. Experimental results demonstrate that the proposed edge detection method can obtain more accurate edge location and reduce false edges, compared with the Canny method，the method based on wavelet and Canny, the method based on contourlet modulus maxima, and the method based on improved (ROEWA). The obtained river edges are complete and clear.
To cope with the problems that edge detection operators are liable to make the detected edges too blurry for synthetic aperture radar (SAR) images, an edge detection method for detecting river in SAR images is proposed based on contourlet modulus maxima and improved mathematical morphology. The SAR image is firstly transformed to a contourlet domain. According to the directional information and gradient information of directional subband of contourlet transform, the modulus maximum and the improved mathematical morphology are used to detect high frequency and low frequency sub-image edges, respectively. Subsequently, the edges of river in SAR image are obtained after fusing the high frequency sub-image and the low frequency sub-image. Experimental results demonstrate that the proposed edge detection method can obtain more accurate edge location and reduce false edges, compared with the Canny method，the method based on wavelet and Canny, the method based on contourlet modulus maxima, and the method based on improved (ROEWA). The obtained river edges are complete and clear.
2014, 31(5):484-491.
Abstract:
A fully flexure micro/nano transmission platform (MNTP) which has five degrees of freedom is designed on the basis of bridge type amplification mechanism. According to the kinematic theory and the elastic beam theory, the theoretical output displacement equation of the platform is derived, and then piezoelectric actuator (PZT) is calibrated. Meanwhile, a full closed-loop control strategy of the platform is established using the feedforward proportional integral derivative (PID) compound control algorithm based on the Preisach model. Moreover, the total transfer function of the micro positioning system is derived, and the calculation method of output signal is acquired. Finally, the theoretical output displacement is verified by finite element analysis (FEA) and positioning experiments.
A fully flexure micro/nano transmission platform (MNTP) which has five degrees of freedom is designed on the basis of bridge type amplification mechanism. According to the kinematic theory and the elastic beam theory, the theoretical output displacement equation of the platform is derived, and then piezoelectric actuator (PZT) is calibrated. Meanwhile, a full closed-loop control strategy of the platform is established using the feedforward proportional integral derivative (PID) compound control algorithm based on the Preisach model. Moreover, the total transfer function of the micro positioning system is derived, and the calculation method of output signal is acquired. Finally, the theoretical output displacement is verified by finite element analysis (FEA) and positioning experiments.
2014, 31(5):492-497.
Abstract:
In laser milling assisted with jet electrochemical machining (LMAJECM), the source of energy is a pulsed laser beam aligned coaxially with a jet of electrolyte, which focuses optical energy on the surface of workpiece. The impact of jet of electrolyte develops a state-of-art work to perform operations such as electrolytic etching, effective cooling, and transportation of debris. Therefore, a special jet cell is designed to obtain stable jet as to be a kind of noncontact tool, i.e., electrode. According to the theoretical model of on-off pulse time process, laser machining and electrolytic anodization are simulated by finite element analysis (FEA) method. Grooves on a 0.5 mm thick 321 stainless steel sheet produced by LMAJECM is performed with pulsed Nd:YAG laser at the second harmonic wavelength. Compared with laser milling under ambient atmosphere conditions, the recast layer and burrs are effectively diminished. And the accuracy of depth is dedicated to laser milling, whilst that of width is dominated by jet electrochemical machining. It is demonstrated that LMAJECM can be a highly potential approach for fabricating 3-D micro components.
In laser milling assisted with jet electrochemical machining (LMAJECM), the source of energy is a pulsed laser beam aligned coaxially with a jet of electrolyte, which focuses optical energy on the surface of workpiece. The impact of jet of electrolyte develops a state-of-art work to perform operations such as electrolytic etching, effective cooling, and transportation of debris. Therefore, a special jet cell is designed to obtain stable jet as to be a kind of noncontact tool, i.e., electrode. According to the theoretical model of on-off pulse time process, laser machining and electrolytic anodization are simulated by finite element analysis (FEA) method. Grooves on a 0.5 mm thick 321 stainless steel sheet produced by LMAJECM is performed with pulsed Nd:YAG laser at the second harmonic wavelength. Compared with laser milling under ambient atmosphere conditions, the recast layer and burrs are effectively diminished. And the accuracy of depth is dedicated to laser milling, whilst that of width is dominated by jet electrochemical machining. It is demonstrated that LMAJECM can be a highly potential approach for fabricating 3-D micro components.
2014, 31(5):498-507.
Abstract:
Revolution radius is one of the significant parameters in orbital drilling, which has great influence on many factors, such as the cutting area of front and side cutting edge, undeformed chip geometry, delamination and burr at hole exit side, hole surface roughness, cutting tool force and deflection, chip removal and heat transmission. First, the influence of revolution radius on the factors is discussed theoretically in detail. Analysis results show that big revolution radius can reduce axial cutting force, restrain exit delamination and burr, and improve chip removal and heat transmission. Then, single factor test and orthogonal test are utilized in the two processing methods as machining unidiameter holes with several cutting tools and machining different diameter holes with one tool. Finally, the influence of revolution radius on cutting force and hole machining precision is studied. These results provide a profound foundation for future optimization of cutting control parameters.
Revolution radius is one of the significant parameters in orbital drilling, which has great influence on many factors, such as the cutting area of front and side cutting edge, undeformed chip geometry, delamination and burr at hole exit side, hole surface roughness, cutting tool force and deflection, chip removal and heat transmission. First, the influence of revolution radius on the factors is discussed theoretically in detail. Analysis results show that big revolution radius can reduce axial cutting force, restrain exit delamination and burr, and improve chip removal and heat transmission. Then, single factor test and orthogonal test are utilized in the two processing methods as machining unidiameter holes with several cutting tools and machining different diameter holes with one tool. Finally, the influence of revolution radius on cutting force and hole machining precision is studied. These results provide a profound foundation for future optimization of cutting control parameters.
2014, 31(5):508-514.
Abstract:
Residual stresses can have a strong effect on the usability of machined parts, and the X ray diffraction (XRD) measuring equipment, which is commonly used to measure residual stresses, is very expensive. This paper presents a method of easuring the residual stresses induced by boring in the internal surface of a tube with much cheaper equipment. The method, called the strain-based method is mainly based on the strains measured on the external surface of the tube. It is proposed on the basis of the very long tube assumption. The finite element method (FEM) analysis is thus used to validate the length of the tube. Guided by the FEM results, an appropriate length of the tube is chosen, and the residual stresses are obtained from both the strain based method and the XRD method. Stress profiles obtained from both two methods are compared. The comparison result indicates that the profiles of the two methods agree well with each other. Therefore, it can be concluded that the accuracy of the strain based method is high enough, and it can be applied to residual stress measurement in practice.
Residual stresses can have a strong effect on the usability of machined parts, and the X ray diffraction (XRD) measuring equipment, which is commonly used to measure residual stresses, is very expensive. This paper presents a method of easuring the residual stresses induced by boring in the internal surface of a tube with much cheaper equipment. The method, called the strain-based method is mainly based on the strains measured on the external surface of the tube. It is proposed on the basis of the very long tube assumption. The finite element method (FEM) analysis is thus used to validate the length of the tube. Guided by the FEM results, an appropriate length of the tube is chosen, and the residual stresses are obtained from both the strain based method and the XRD method. Stress profiles obtained from both two methods are compared. The comparison result indicates that the profiles of the two methods agree well with each other. Therefore, it can be concluded that the accuracy of the strain based method is high enough, and it can be applied to residual stress measurement in practice.
2014, 31(5):515-520.
Abstract:
The wear behaviour of composite coatings is related to the nature of embedded particles. The effects of particle size on the wear behaviour of composite coatings are analyzed. Electroless nickel composite coatings containing diamond particles with the sizes in the range of 0—0.5, 0.5—1, 1—2 μm are prepared. The surface morphology of diamond particles and composite coatings are observed by scanning electron microscopy (SEM). The wear tests of composite coatings are comparatively evaluated by sliding against a cemented tungsten carbide ball. The 3D morphology of worn scar is evaluated by using a 3D profiler. The results show that the hardness and wear resistance of composite coatings can increase with the increase of particle sizes. The mixture mechanism of adhesive wear and abrasive wear turn into single abrasive wear with the increase of particle sizes as well. The transformation of wear behaviour is mainly attributed to particle roles during wear process.
The wear behaviour of composite coatings is related to the nature of embedded particles. The effects of particle size on the wear behaviour of composite coatings are analyzed. Electroless nickel composite coatings containing diamond particles with the sizes in the range of 0—0.5, 0.5—1, 1—2 μm are prepared. The surface morphology of diamond particles and composite coatings are observed by scanning electron microscopy (SEM). The wear tests of composite coatings are comparatively evaluated by sliding against a cemented tungsten carbide ball. The 3D morphology of worn scar is evaluated by using a 3D profiler. The results show that the hardness and wear resistance of composite coatings can increase with the increase of particle sizes. The mixture mechanism of adhesive wear and abrasive wear turn into single abrasive wear with the increase of particle sizes as well. The transformation of wear behaviour is mainly attributed to particle roles during wear process.
2014, 31(5):521-529.
Abstract:
To optimize cutting control parameters and provide scientific evidence for controlling cutting forces, cutting force modeling and cutting control parameter optimization are researched with one tool adopted to orbital drill holes in aluminum alloy 6061. Firstly, four cutting control parameters(tool rotation speed, tool revolution speed, axial feeding pitch and tool revolution radius) and affecting cutting forces are identified after orbital drilling kinematics analysis. Secondly, hybrid level orthogonal experiment method is utilized in modeling experiment. By nonlinear regression analysis, two quadratic prediction models for axial and radial forces are established, where the above four control parameters are used as input variables. Then, model accuracy and cutting control parameters are analyzed.Upon axial and radial forces models, two optimal combinations of cutting control parameters are obtained for processing a 13 mm hole, corresponding to the minimum axial force and the radial force respectively. Finally, each optimal combination is applied in verification experiment. The verification experiment results of cutting force are in good agreement with prediction model, which confirms accracy of the research method in practical production.
To optimize cutting control parameters and provide scientific evidence for controlling cutting forces, cutting force modeling and cutting control parameter optimization are researched with one tool adopted to orbital drill holes in aluminum alloy 6061. Firstly, four cutting control parameters(tool rotation speed, tool revolution speed, axial feeding pitch and tool revolution radius) and affecting cutting forces are identified after orbital drilling kinematics analysis. Secondly, hybrid level orthogonal experiment method is utilized in modeling experiment. By nonlinear regression analysis, two quadratic prediction models for axial and radial forces are established, where the above four control parameters are used as input variables. Then, model accuracy and cutting control parameters are analyzed.Upon axial and radial forces models, two optimal combinations of cutting control parameters are obtained for processing a 13 mm hole, corresponding to the minimum axial force and the radial force respectively. Finally, each optimal combination is applied in verification experiment. The verification experiment results of cutting force are in good agreement with prediction model, which confirms accracy of the research method in practical production.
2014, 31(5):530-537.
Abstract:
A new control algorithm is presented for digitally controlled dc-dc converters to achieve a fast response under a successive load change. Under the steady state condition, the tight voltage regulation is processed by the conventional digital PID compensator. If the load disturbance is significant, the controller switches to an optimal control scheme. With the integration of the capacitor current, the proposed algorithm predicts the optimal switch over time based on the charge balance control, and the minimal voltage derivation and recovery time are thus achieved when the load current has a successive load change. The method for calculating the optimal switch over time is described, and the implementation of the proposed algorithm with a digital controller is treated in detail. Furthermore, the simulation and experiment results are provided to validate the effectiveness of the approaches.
A new control algorithm is presented for digitally controlled dc-dc converters to achieve a fast response under a successive load change. Under the steady state condition, the tight voltage regulation is processed by the conventional digital PID compensator. If the load disturbance is significant, the controller switches to an optimal control scheme. With the integration of the capacitor current, the proposed algorithm predicts the optimal switch over time based on the charge balance control, and the minimal voltage derivation and recovery time are thus achieved when the load current has a successive load change. The method for calculating the optimal switch over time is described, and the implementation of the proposed algorithm with a digital controller is treated in detail. Furthermore, the simulation and experiment results are provided to validate the effectiveness of the approaches.
2014, 31(5):538-545.
Abstract:
The aim of this work is to analyze and design a control system for vibration reduction in a rotor system using a shear mode magnetorheological fluid (MRF) damper. A dynamic model of the MRF damper rotor system was built and simulated in Matlab/Simulink to analyze the rot or vibration characteristics and the vibration reduction effect of the MRF damper. Based on the numerical simulation analysis, an optimizing control strategy using pattern search method was proposed and designed. The control system was constructed on a test rotor bench and experiment validations on the effectiveness of the proposed control strategy were conducted. Experimental results show that rotor vibration caused by unbalance can be well controlled whether in resonance region (70%) or in non-resonance region (30%). An irregular vibration amplitude jump can be suppressed with the optimization strategy. Furthermore, it is found that the rapidity of transient response and efficiency of optimizing technique depend on the pattern search step. The presented strategies and control system can be extended to multi-span (more than two or three spans) rotor system. It provides a powerful technical upport for the extension and application in target and control for shafting vibration.
The aim of this work is to analyze and design a control system for vibration reduction in a rotor system using a shear mode magnetorheological fluid (MRF) damper. A dynamic model of the MRF damper rotor system was built and simulated in Matlab/Simulink to analyze the rot or vibration characteristics and the vibration reduction effect of the MRF damper. Based on the numerical simulation analysis, an optimizing control strategy using pattern search method was proposed and designed. The control system was constructed on a test rotor bench and experiment validations on the effectiveness of the proposed control strategy were conducted. Experimental results show that rotor vibration caused by unbalance can be well controlled whether in resonance region (70%) or in non-resonance region (30%). An irregular vibration amplitude jump can be suppressed with the optimization strategy. Furthermore, it is found that the rapidity of transient response and efficiency of optimizing technique depend on the pattern search step. The presented strategies and control system can be extended to multi-span (more than two or three spans) rotor system. It provides a powerful technical upport for the extension and application in target and control for shafting vibration.
2014, 31(5):546-551.
Abstract:
The theoretical solutions are obtained for the three-dimensional (3-D) stress field in an infinite isotropic elastic plate with a through the thickness circular hole subjected to shear load at far field by using Kane and Mindlin′s assumption based on the stress function method. Based on the present solutions, the characteristics of 3-D stress field are analyzed and the emphasis is placed on the effects of the plate thickness and Poisson′s ratio on the deviation of the present 3-D in plane stress from the related plane stress solutions, the stress concentration and the out-of-plane constraint. The present solutions show that the stress concentration factor reaches its peak value of about 8.9% which is higher than that of the plane stress solutions. As expected, the out-of-plane stress constraint factor can reach 1 on the surface of the hole when the plate is a very thick one.
The theoretical solutions are obtained for the three-dimensional (3-D) stress field in an infinite isotropic elastic plate with a through the thickness circular hole subjected to shear load at far field by using Kane and Mindlin′s assumption based on the stress function method. Based on the present solutions, the characteristics of 3-D stress field are analyzed and the emphasis is placed on the effects of the plate thickness and Poisson′s ratio on the deviation of the present 3-D in plane stress from the related plane stress solutions, the stress concentration and the out-of-plane constraint. The present solutions show that the stress concentration factor reaches its peak value of about 8.9% which is higher than that of the plane stress solutions. As expected, the out-of-plane stress constraint factor can reach 1 on the surface of the hole when the plate is a very thick one.
2014, 31(5):552-558.
Abstract:
The parachute container cover ejection separation is the first and foremost motion for the return capsule recovery system, which is related to the success of a recovery system. Adopting the computational fluid dynamics(CFD) simulation and flight dynamics coupling method, the parachute container cover ejection separation is simulated. The rationality of the ejection separation speed and dynamic characteristics of the separation process is analyzed. Meanwhile, the influences of angle of attack, Mach number and ejection separation speed on the parachute container cover ejection are also investigated. Results show that the ejection separation speed design is reasonable. It has a certain design margin for parachute container cover to escape from the wake region, and to pull out the drag parachute completely. The results may provide a theoretical basis for recovery system engineering design of the lunar exploration project.
The parachute container cover ejection separation is the first and foremost motion for the return capsule recovery system, which is related to the success of a recovery system. Adopting the computational fluid dynamics(CFD) simulation and flight dynamics coupling method, the parachute container cover ejection separation is simulated. The rationality of the ejection separation speed and dynamic characteristics of the separation process is analyzed. Meanwhile, the influences of angle of attack, Mach number and ejection separation speed on the parachute container cover ejection are also investigated. Results show that the ejection separation speed design is reasonable. It has a certain design margin for parachute container cover to escape from the wake region, and to pull out the drag parachute completely. The results may provide a theoretical basis for recovery system engineering design of the lunar exploration project.
13 Solving Job Shop Scheduling Problem Based on Improved Adaptive Particle Swarm Optimization Algorithm
2014, 31(5):559-567.
Abstract:
An improved adaptive particle swarm optimization (IAPSO) algorithm is presented for solving the minimum makespan problem of job shop scheduling problem (JSP). Inspired by hormone modulation mechanism, an adaptive hormonal factor (HF), composed of an adaptive local hormonal factor (Hl) and an adaptive global hormonal factor (H-g), is devised to strengthen the information connection between particles. Using HF, each particle of the swarm can adjust its position self-adaptively to avoid premature phenomena and reach better solution. The computational results validate the effectiveness and stability of the proposed IAPSO, which can not only find optimal or close-to-optimal solutions but also obtain both better and more stability results than the existing particle swarm optimization (PSO) algorithms.
An improved adaptive particle swarm optimization (IAPSO) algorithm is presented for solving the minimum makespan problem of job shop scheduling problem (JSP). Inspired by hormone modulation mechanism, an adaptive hormonal factor (HF), composed of an adaptive local hormonal factor (Hl) and an adaptive global hormonal factor (H-g), is devised to strengthen the information connection between particles. Using HF, each particle of the swarm can adjust its position self-adaptively to avoid premature phenomena and reach better solution. The computational results validate the effectiveness and stability of the proposed IAPSO, which can not only find optimal or close-to-optimal solutions but also obtain both better and more stability results than the existing particle swarm optimization (PSO) algorithms.
2014, 31(5):568-575.
Abstract:
Acquisition of real-time and accurate vehicle state and parameter information is critical to the research of vehicle dynamic control system. By studying the defects of the former Kalman filter based estimation method, a new estimating method is proposed. First the nonlinear vehicle dynamics system, containing inaccurate model parameters and constant noise, is established. Then a dual unscented particle filter (DUPF) algorithm is proposed. In the algorithm two unscented particle filters run in parallel, states estimation and parameters estimation update each other. The results of simulation and vehicle ground testing indicate that the DUPF algorithm has higher state estimation accuracy than unscented Kalman filter (UKF) and dual extended Kalman filter (DEKF), and it also has good capability to revise model parameters.
Acquisition of real-time and accurate vehicle state and parameter information is critical to the research of vehicle dynamic control system. By studying the defects of the former Kalman filter based estimation method, a new estimating method is proposed. First the nonlinear vehicle dynamics system, containing inaccurate model parameters and constant noise, is established. Then a dual unscented particle filter (DUPF) algorithm is proposed. In the algorithm two unscented particle filters run in parallel, states estimation and parameters estimation update each other. The results of simulation and vehicle ground testing indicate that the DUPF algorithm has higher state estimation accuracy than unscented Kalman filter (UKF) and dual extended Kalman filter (DEKF), and it also has good capability to revise model parameters.
2014, 31(5):576-579.
Abstract:
The effect of Gurney flaps with different heights on the S809 airfoil and NH1500 blade is numerically simulated. The influence of the Gurney flap is analyzed at different wind speeds and the comparison of the aerodynamic performance is given between the blades with and without the Gurney flap. The results demonstrate that a Gurney flap added on the blade can greatly increase the efficiency of the wind turbine especially at high wind speeds.
The effect of Gurney flaps with different heights on the S809 airfoil and NH1500 blade is numerically simulated. The influence of the Gurney flap is analyzed at different wind speeds and the comparison of the aerodynamic performance is given between the blades with and without the Gurney flap. The results demonstrate that a Gurney flap added on the blade can greatly increase the efficiency of the wind turbine especially at high wind speeds.
2014, 31(5):580-588.
Abstract:
In order to obtain accurate conflict risks in terminal airspace design, the concept and calculation model of potential conflict frequency for intersected routes are proposed. Conflict frequency is represented by the product of horizontal conflict frequency and vertical conflict probability. The horizontal conflict frequency is derived from the probability density distribution of conflicts in a period of time. Based on the recorded radar trajectory data, the concept and model of ROUTE distance are proposed, and the probability density function of aircraft height at a specified ROUTE distance is deduced by kernel density estimation. Furthermore, vertical conflict probability and its horizontal distribution are achieved. Examples of three intersected arrival and departure route design schemes are studied. Compared with scheme 1, the conflict frequency values of the other two improved schemes decrease to 53% and 24%, respectively. The results show that the model can quantify potential conflict frequency of intersected routes.
In order to obtain accurate conflict risks in terminal airspace design, the concept and calculation model of potential conflict frequency for intersected routes are proposed. Conflict frequency is represented by the product of horizontal conflict frequency and vertical conflict probability. The horizontal conflict frequency is derived from the probability density distribution of conflicts in a period of time. Based on the recorded radar trajectory data, the concept and model of ROUTE distance are proposed, and the probability density function of aircraft height at a specified ROUTE distance is deduced by kernel density estimation. Furthermore, vertical conflict probability and its horizontal distribution are achieved. Examples of three intersected arrival and departure route design schemes are studied. Compared with scheme 1, the conflict frequency values of the other two improved schemes decrease to 53% and 24%, respectively. The results show that the model can quantify potential conflict frequency of intersected routes.
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